Background Anxiety is common after acute myocardial infarction and increases the number of complications and the length of stay in the hospital. Anxiety-induced activation of the sympathetic nervous system is hypothesized to be an underlying cause of increased complication rates. Little is known about whether use of β-blockers eliminates the effects of anxiety on complication rate and length of stay. Objective To compare number of complications and length of stay among nonanxious and anxious patients receiving β-blockers during hospitalization. Method A total of 322 patients with acute myocardial infarction participated in this study within 48 hours of hospital admission. Patients completed the Brief Symptom Inventory to assess anxiety level. After discharge, medical records were reviewed to determine use of β-blockers, type and number of complications, and length of stay. Results Most patients (96%) were treated with less than 200 mg daily of metoprolol. Anxious patients had more complications (mean [SD], 1.43 [0.15] vs 0.73 [.09], P = .01) and longer stays (7.0 [0.49] vs 5.7 [0.36] days, P < .05) than did nonanxious patients. To test whether the dose of β-blocker made a difference, the interaction between daily dose and anxiety score was tested. No interaction was found between metoprolol dose and anxiety score, and no main effect was found for metoprolol dose. Conclusion Anxious patients had more complications and longer stays than did nonanxious patients. The administration of metoprolol did not eliminate this relationship, perhaps because patients did not receive a sufficient dose of metoprolol to counter the effect of anxiety.